A laser array light source unit that emits a plurality of laser beams may be used as a light source. Further, as a method for adjusting the beam-to-beam distances between a plurality of laser beams, at least one of the adjustment methods using a combination of a plurality of optical lenses as referred to in Japanese Patent Publication No. JP-A-2004-86019, Japanese Patent Publication No. JP-A-9-21972, and Japanese Patent Publication No. JP-A-5-13297 may be used.
However, when a plurality of optical lenses are combined and used as described in the above identified methods, the characteristics of each optical lens need to be close to specified values and the optical lenses need to be assembled in a highly accurate manner. For example, existing technology configurations often face the difficult task of adjusting the beam-to-beam distance with sufficient accuracy; often these adjustments are as small as 1 mm or smaller. Further, the use of a plurality of optical lenses may increase the size of the laser light source. Such difficulties not only occur where a plurality of laser beams are used, but also commonly occur where a plurality of light beams are used.